1. Field of the Invention
The present invention relates to a chaotic signal generator for an ultra wide band communication system, and more particularly which incorporates an inverter type amplifier in order to reduce chip size over a conventional LC type, save unit costs of products and increase yield with superior reproducibility.
2. Description of the Related Art
In general, a chaotic signal is characterized as an aperiodic signal with no phase, and a wide band signal. A typical periodic signal has a regular phase in accordance with time and thus may be distorted or cancelled when an interference signal of an antiphase is added. However, a chaotic signal has no clear phase so that it does not interfere with any antiphase signals or proximal interference signals, even if induced thereto. This serves to protect information in the signal.
Also, at a frequency domain, the chaotic signal is uniformly sized regardless of a cycle in a wide band and exhibits superior energy efficiency.
Such a chaotic signal can be made suitable for information transmission and utilized as a carrier wave. This eliminates a need for a separate coding such as time hopping in a modem due to fewer spikes, also allowing simple configuration of a transceiver via a simple modulation method of On-Off keying (OOK).
Meanwhile, by a conventional modulation method using the chaotic signal, in principle, it is possible to transmit signals via a bandwidth corresponding to 10% to 20% of a carrier frequency band. But disadvantageously the conventional modulation method is accompanied by considerably complicated technical interpretations.
Notwithstanding such drawbacks, attempts have been made to utilize the chaotic signal due to significant advantages thereof. One advantage is that the chaotic signal ensures a communication system with higher power efficiency owing to their controllability through a small change in the system. Another advantage is that the chaotic signal fundamentally has a continuous spectrum which expands into a wider frequency bandwidth, thus applicable to the modulation where an energy spectrum is required to have no loss throughout the wide bandwidth.
FIG. 1 is a circuit diagram of a conventional chaotic signal generator.
The conventional chaotic signal generator shown in FIG. 1 is a Colpitts-type chaotic signal generator. The chaotic signal generator of FIG. 1 includes a chaotic signal generator 10 for generating a chaotic signal and a band pass filter 20 for passing the chaotic signal from the chaotic signal generator 10 through a specified frequency band.
The chaotic signal generator 10 includes power supplies VC and VE, a transistor Q as an active device for forming non-linear negative resistance to generate the chaotic signal and at least three passive devices for storing energy while delaying time. The passive devices include capacitors CB,C1 and C2, an inductor L and resistors RL and RE. This chaotic signal generator 10 adopts a resonator including an energy storing device such as the inductor L for storing magnetic field energy and the capacitor C for storing electric field energy.
However, the conventional chaotic signal generator employing the resonator including the inductor L and the capacitor C requires a large chip area due to the inductor, thereby disadvantageously increasing the chip price and undermining energy efficiency due to a big energy loss on the inductor caused by CMOS.
Also, the conventional chaotic signal generator disadvantageously has poor reproducibility owing to excessive sensitivity to current when generating the chaotic signal, and lowers product yield.